1. Field of the Invention
The present disclosure is generally related to photometric devices, and particularly but not exclusively relates to photometric devices for performing light absorbance measurements.
2. Description of Related Art
There are several types of photometric devices used in a variety of different applications. In general, photometric devices include devices that are used to measure or otherwise determine one or more properties of light, such as intensity, color, wavelength, or other characteristics.
One type of photometric device is an optical absorbance sensor. One type of optical absorbance sensor is a cell density probe, which is used in biotechnology, chemical, brewery, wine, ethanol, fermentation, pharmaceutical, and other sectors of industry and/or research. With biotech applications, cell density probes are ordinarily used to monitor cell growth in a cell culture. In a typical implementation, live cells and some type of suitable growth agent (as well as possibly other additives) are placed in a vat or other vessel, with the growth agent, cells, and possibly other additives together forming a “broth” made up of liquid and suspended particulates (e.g., the cells). Conditions in the vat are then appropriately controlled to induce the cells to multiply and grow. The cells, once a sufficient amount have been grown, are harvested for various uses.
Cell density probes are used to monitor the cell growth in the vat at various times during the growing cycle, so as to ensure that the cells are growing at a proper rate and/or to verify whether a sufficient number of cells have been grown. Use of a cell density probe is an alternative to manual cell counting techniques, wherein cells in a sample from the vat are extracted and physically counted (and thus result in a high degree of error). In comparison, a density probe allows the number of cells to be automatically determined by correlation of light absorbance to cell density.
A typical cell density probe includes a tip that has an optical gap. The cell density probe is immersed into the vat, such that the optical gap and tip are completely covered by the broth. Light (at a specific wavelength or set of wavelengths) is transmitted from a first end of the optical gap to a second end of the optical gap. As the light passes through the optical gap, the cells present within the optical gap absorb and scatter a certain amount of the light. Therefore, the light received at the second end of the optical gap will have a lower intensity than the light transmitted from the first end of the optical gap, due to the absorbance and scattering of the light by the cells, which is typically expressed in terms of absorbance units (A.U.). The intensity of the received light decreases as the density of cells increase. Persons skilled in the art can correlate various intensities of the received light with growth rates and cell densities for the particular cell type that is involved. Accordingly, by monitoring the intensity of the received light over a period of time, the user of the cell density probe can determine if the growth rate is proceeding normally, if a sufficient number of cells have been grown, and/or whether a problem has occurred in the growing cycle. For example, if at a given wavelength the cell density probe provides a light intensity measurement that is higher than expected for that particular time in the growth cycle, then the higher intensity measurement at that wavelength may be indicative of contamination or other environmental condition that is impeding the capability of the cells to grow properly.
Existing photometric devices suffer from a number of disadvantages for use in biotech applications, including difficulty in manufacturing, bulkiness, unreliable or inefficient illumination components, complex structural parts, and other problems.